The A7r has 36Mp as well as CIZ. 36Mp allows for a 2x zoom, and CIZ would double this again.

Or, mapping A7r down to 16Mp with CIZ allows for a 4x factor. That is, the basic 24-70 could be extended to 280mm FL equiv. using both crop (2x) and CIZ (2x). The OM-D EM-1 needs the 140mm FL for that.

So - look at it this way: 45-150 on OM-D EM-1 vs. 24-70 on Sony A7R. (The 28-70 is slightly smaller, but not in the database yet).

I am also throwing in the Nex-7, with 24Mp, it allows for a 1.5x zoom factor and 2x CIZ, so you'd get 3x conversion. So a 100mm lens would suffice to reach 280mm FL equiv. I am showing it with the 18200LE, which already reaches a 450mm FL equiv. without even applying the CIZ factor. With it it would be 900mm FL equiv. I am adding in the 100-300mm onto the EM-1 for good measure.